Many of the most frequently used depression instruments were created more than 40 years ago, without the benefit of rigorous psychometric development and testing. Most of these measures were designed to provide only a single overall index of depression, so that they do not yield reliable and valid subscales assessing specific types of depressive symptoms. Furthermore, progress in this area is hampered by our limited understanding of the internal structure of depressive symptoms. The proposed work will result in a multi-dimensional measure of depression that will include a wide range of depression symptoms, as well as symptoms of related anxiety disorders such as generalized anxiety disorder, social phobia, and panic disorder. The scales comprising the final measure will be suitable for use in clinical outcome research as well as other studies of the etiology and consequences of depression. The process will begin with the creation of a comprehensive item pool; our review of the literature indicates that this pool should multiple groups of items assessing prominent symptoms of depression, another group of items measuring positive emotionality, and several clusters of anxiety-related items. These items will undergo extensive testing with diverse samples of both clinical and non-clinical adult populations. The goal of the initial phases of the proposed research is to determine the factor structure of depression and related symptoms so that appropriate subscales are modeled in the final measure. Further studies will assess the construct validity of the resulting factor-based measures through analyses of their (a) sensitivity to change and (b) convergence with other self-report and clinician-rated measures of depression and anxiety. The next group of proposed studies will use advanced psychometric methods (including confirmatory factor analysis and item response theory) to assess the suitability of the measure--at both the subscale and item level--in different populations (e.g., adolescents, pregnant and postpartum women, and older adults) and to modify the instrument as necessary for use with these populations.